1. Field of the Invention
The present invention relates to the mechanisms for forming the shed in weaving looms, and more particularly to the dobbies of the rotating type, i.e. in which the control of the reciprocating vertical displacement of each heddle frame is ensured by means of an oscillating rod of which one end is coupled to the frame while the opposite end, cut out with an opening, is engaged on an actuating eccentric.
2. History of the Related Art
Applicants' French Patent No. 80 06545 (2 478 682) filed on Mar. 20, 1980 discloses rotating dobbies in which the eccentric, mounted idly on a shaft which is rotated with a stop every 180.degree., is laterally secured with a projecting plate which provides support for a coupling member intended to link the shaft to the eccentric angularly, at the opportune moment, in order to effect displacement of the rod and of the frame coupled thereto. This coupling member, thus placed outside the eccentric, is an articulated hook which is subjected, against elastic return means, to the action of one or the other of two pivoting selector levers actuated by the reading device of the dobby, as a function of the program incorporated in the reading device. Each of the two opposite ends of the hook comprises a nose element adapted to cooperate with one or the other of two notches made in a drive disc angularly secured to the shaft which rotates intermittently.
It will be understood that, when one of the nose elements of the hook is engaged by the elastic return means inside one of the notches of the drive disc, the eccentric is angularly linked to the shaft and effects actuation of the rod. On the contrary, when one of the pivoting selector levers comes into abutment against the hook, there is no more coupling and the eccentric is therefore not displaced by the shaft, with the result that the rod is not controlled; as, in this position, the other nose element of the hook is engaged in a notch made in an annular boss on the rod. The rod is angularly connected to the eccentric through the hook and is consequently immobilized, thus avoiding any parasitic displacement of the rod under the effect of the weight of the corresponding heddle frame.